Secrecy intercommunicating telephone system.



W. P. ANDRICK.

SECRECY INTERCOIVIMUNICATING TELEPHONE SYSTEM.

APPLICATION FILED DEC. 9. I912.

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WITNESS/:"8

WALLACE PEAU ANDRICK, or JAMAICA, NEW YORK, AssIGNOMf-'BMMES'NE Y"ASSIGN- MNN'rs, 'ro GENERAL Aoousric' COMPANY, A CORPORATION 'or New YORK.

SECRECY INTERCOMMUNICATING TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Apr. 25, that@ Application filed December 9, 1912. Serial No. 735,621.

munication had merely a single pair of tele phones which were disconnected from,r any other station. Another secrecy system hitherto used has involved the use ot' la relay which has had a number of contacts, and which systemalso involved the use or" a dial with division contacts and intermediate contacts which were connected to a second relay which was thrown by the movement of the dial.- Other systems hitherto used have imposed additional service requirements On the duty of the operators which is objectionable. The main object of the present invention is to' provide a system which is completely secret but in which there is no more manipulation of service on the partot` the operator` x than 1s present 1n any ordmary mtercc-mmunic-ating telephone system.

A further object of the present invention is to provide a secrecy intercommunicating telephone system in which there is a minimum number of contacts both in thev keys, and inthe relay, and in which the circuits are involved.

A further objectoil the present invention is to provide a system which is completely secret not only for the usual conditions of service but also for extraordinary conditions which arise only occasionally by chance.

A still further object of the present invention is to provide a system which is sim ple, cheap to construct and to install anddurable.

lVith these objects'in view the invention consists in the improved secrecy telephone system as hereinafter set forth and claimed. ln the drawings Figure 1 is a diagramvmatic view showing a complete system and all the circuits thereof, as embodying the generally direct and simple and noti invention. Fig. 2 is a sectional view showing a mechanical detail. Fig. 3 is a fragmentary view showing one of the station keys and the switch-hook and associated parts, the front casing being removed for the sake of clearness.

The present inventionl provides a system including any number of stations A, B, C, etc., of which three are illustrated in the drawing. rlthe instruments include the usual transmitter l, receiver 2, and a call bell or buzzer 3 which rings by a direct current. There is also one relay 4 with three contacts. There is also in each instrument a group of manually controlled keys 5 or any suitable station selecting devices, the number of which will ordinarily be one less than the number' of stations, each having two contacts. Each station also has a ringing key 6 with two contacts, one which is made and one which is broken by either movement of the key.` Also at each station there is a switch hook 7 having two 4upper contacts which are broken and a lower contact which is completed when the receiver is on the hook. There is also resistances 8, 9, one having, say fifty ohms and the other perhaps l100 ohms of non-inductive resistance,

as an example. Two batteries 10, 11, are provided in the system, one foi-the. ringing circuits and one for the talking circuits. n

The system is used like a non-secret or ordinary intercommunicating telephone, that/is to say, any party takes his receiver oit' the hook displaces the station selecting key, and then presses the ringing key. The party called removes his receiver and talks. In the meantime any other person of the system, pressing a key to call either of the communicating parties, can not complete any circuit which will affect the stations connected. ln other words, he will not complete any ringing circuit` or talking circuit with either' of these two stations. The fact that he does not hear any buzzer induction effect shows that he is on a busy line, for he would hear the effect of the ring in case he called a party who is not busy in a normal way. Another indication would be provided by his own home relay which normally gives a certain click, but which does not give any click whenthe busy wire is called. This relay, as described,xis characteristic .of this secret system, and has no counterpart in any other secret system.

In the event that A tried to call C while B is calling C then both A and B would be put on Cs circuit, and all can talk together, but this contingency is dependent on the mere chance that A happens to ring at the precise instant after B has rung C, and before C responds. In the meantime A has rung Cs buzzer and B who is listening will hear this and be advised that another party is in a position to hear. Thus B is advised of the possibility of the secrecy being inter- Jfered with and can call C again later. The same would be true if vunder the same circumstances AVI-tried to call B while C was calling B.

Any stationin order to get a connection must necessarily ring the buzzer at that station, so that it is not possible to get in on the line without having given an indication which might be investigated. Furthermore, if an attempt is made to leave the receiver oft' the hook permanently, that station cann not be called and this fact will of course quickly lead to an investigation, so that it `is not possible for any person either to listen in from time to time by taking a receiver off the hook at intervals, nor is it possible to listen in by leaving the receiver off the hook all the time after having given a signal and not responded to the answer or not hung up after actually talking without the fact soon becoming known. l

The present system operates broadly on the principle of having to ring before it is possible to get a telephone connection, the ringing operating the relay at the calling station that establishes the telephone circuit.

There will be a pair of wires foreach station of the system, these wires running common to all the stations. There are also four extra wires of which two are connected with a talking battery and the other two to a ringing battery. Three stations are shown of a ive station system, there being four keys at each station necessary to call the outer four stations of the system. An extra pair of wires has been illustrated indicating the fact that extra Wires and stations may be added, it being merely necessary to add an extra key and connections to the extra pair of wires.

When any station, for instance station A calls another station, for example C, A will of course remove the receiver from the hook, and displace the station C key. As ringing key Will'also be pressed to move the blade upward. Current flows from thenegative pole of battery 10 through wire Z1, Wires Z2, Z3, relay magnete, wire Z4, wire Z5, contact Z",'Wire Z7, contact Z8, wire Z", cable Wire c1, wire Z1, contact Z, buzzer 3, wire Z, back to the battery. It will be observed that this circuit includes the magnet 4 of As relay, and the buzzer 3 of Cs station.

The energizing of relay 4 at station A has an initial effect of allowing solne current to flow through a slightly changed circuit, so that Cs buzzer may ring with the full available strength of the battery. This prevents possibility of failure to ring by reason of the resistance and reactance oi' the relay. A low reactance shunt is established across the relay coil from wire Z" by means of the contact m1, wire m2, resistance 8, wire m3 to the circuit wire Z3. By putting the low resistance 8 in shunt with the relay magnet el, there is of course a double path provided and the low reaetance leg insures sufiicientcurrent. At the same time the resistance 8 insures a slight potential difierence across the relay magnet 4f to keep it energized enough to hold its armature. It is to be particularly understood that the impedance of the relay magnet is the main source ot difficulty because of the pulsating current required in the buzzer. ance 8 is a non-inductive resistance, and may be comparatively high in ohmic value. and still give the effects just described. i Tt may be assumed that A will now release his ringing key 6, but a circuit has already been established maintaining the relay magnet l energized, so that this energization continues notwithstanding the release of the ringing key 6. This circuit is as follows: battery l0, wire Z1, wire Z2, wire Z3, relay magnet 4,'wire Zt, contact ml, large ohmic resistance 9, and contact 01 hereinafter described, which is closed by the removal of As receiver from the switch book, wire o2, back to positive battery. Tt will be observed that this circuit does not include the ringing key, so that the circuit continues regardless of the release of the ringing keyr The ringing is now complete and the matter of getting a current for Cs buzzer is of course of no further interest. The only matter of interest now is maintaining the relaymagnet 4 sufficiently energized to hold its armature, and this will be done through the large ohmic resistance 9 in series with the relay magnet 4. The ohmic resistance 8 is of sufiicient magnitude to insure suiiicient potential across the relay to prevent the release of the relay armature notwithstanding the interposition of the high resistance 9, the line cable to and the buzzer at the called station having by this time been cut out of the circuit by the release of the ringing key at the calling station. C removes the receiver from the hook and talking circuits are established as follows talking negative battery 11, wire p1, wire 772, through the usual retardation coil R, wire p3, transmitter l, and receiver 2 of station A, switch hook, wire y2", coil R, and wire 7) to positive battery. This circuit produces the usual potential fluctuations across the The resist- 4 meente i receiver and transmitter, due to the changing resistances of this part of the circuit, and these voice currents are impressed on the line to station C through the following circuit: wire g1,contact g2, wire g3, contact g4, wire g5, cable wire c2, wire Q6, through the transmitter and receiver of station C, down wire Z1", back to cable wire 01, wire Z9, contact Z8, wire Z7, lower spring blade Q7, wire ticularly to the secrecy features by which any station is prevented from cutting in on a busy line and hearlng the conversation or taking part in it.

When the communication is concluded it is of course necessary to restore the circuits to their original normal condition, because since As relay has been operated by calling C it is evidently in condition to either call or listen on some` other station after `getting through with C. llt will be understood that communication could not have been had with C in the first instance, without actually calling C, but after the relay has been operated as described, circuits for' possible communication might evidently be had with some other station Without actually calling that station, unless means were provided to prevent this. This is accomplished as follows: Assuming that C hangs up his receiver, and A for any reason may or may not restore the key for station C, it may be assumed for example that he displaces another key, for example that for station B. This will not put him in communication with B through the energized relay 4 already described, because he is obliged to displace the` station B key and by this the relay 1 is restored to normal and natural circuit condi-` tions already described.

`When any station key is displaced, for eX- ample that-for station B, even without As placing his receiver back on the hook, the

' Contact o1 is momentarily broken as hereinafter described, and as the entire current for maintaining the relay 4 energized flows .through this contact it is evident that the relay releases its armature the instant that it manipulates any key. 1n other words, the circuits are restored to normal condition. A cannot then get B by any other method, except by definitely calling B, in which case B will respond in the usual way.

llf already busy B cannot be either called or talked to since the ringing circuit is open when the receiver is off the switch-hook and for which reason the relay at the calling station can not'be energized to complete the talking circuits.

It is an important principle of the present invention that the contact 01 is broken under certain determined conditions, that is, when the receiver is hung up and also when any station key is moved or displaced in either direction. Referring now to Figs. 2 and 3, a construction is shown similar to that disclosed. in U. S. Letters Patent No. 1,081,712, granted Dec. 1 6, 1913, which discloses a construction whereby this result is obtained and comprises broadly a recipro- `cating link 13 which is connected at one end p to a pivoted switch-hook 13 upon which the receiver normally hangs. The link 13 is connected by means of a lost motion connection with a universal detent bar 14 having the ends thereof bent inwardly to form ears `by which the detent bar is pivoted to the casing as at 14:1. rlhis bar constitutes the detent for positively maintaining each of the station keys in either of its displaced positions, and it may be here stated that in Fig. 2, two sets of contact blades of two of the station keys 5 are arranged one above the other, so that the set of blades corresponding to one station will be closed when the station key is depressed, and the other when the station key is moved in the opposite direction. Bach key comprises a disk-like body 15 having two notches 16 therein in which the universal detent bar 14 falls when the key is in either of its depressed positions to hold it in such position against the tension of the contact blades. When the detent bar is lifted by the depression of the switchhook, the keys will therefore return to their normal or open position under the tension of the contact-blades. Arranged at one end of the series of station keys 5, are two vcontact springs '17 and 18, which have heretofore been referred to as the 'contact 01. rthese contact springs are normally closed and are moved to their open position by the engagement of the contact springs 17 with an insulated bushing 19 carried by the link 13. Upon downward'movement of the link, due to the hanging up of the receiver, the contact spring 17 will be forced out of engagement with the contact spring 18 and hence the contact o1 will be opened. rll`he contact will also be opened when any of the station keys are moved from-their displaced position to their normal positionv by the operator, since the detent b-ar 1,4 will be moved upwardly out of the notch 16 and hence its other end which is connected to the link 13, will move the link 13 and the insulated bushing 19 downward to open the contacts.

In the event that an attempt is made to llt@ come in on a telephone circuit by the expedient of holding one key depressed after having concluded a regular conversation with that station, and at the same time pressing another key to another station the secrecy feature is still preserved because on account of the fact that bar 14 is a universal bar and coperates as described with the keys, the contact 01 is bound to be broken in any case. The expedient. just mentioned will not serve to secretly gain telephonie communication. The only connection which can be established will be a new call to such station and by the use of the calling current as already described.

What is claimed is l. In a secrecy intercommunicating telephone system, a plurality of stations each having a transmitter, receiver, signal, switch hook, and keys for the other stations, talking circuits interconnecting said stations, a common battery for supplying talking current to all of said talking circuits, and a relay at each station in the circuit of the signaling current to any station called, said relay having a contact by which talking circuits from such station to other stations can be exclusively established.

2. In a secrecy intercoinmunicating telephone system, a plurality of stations each having a transmitter, receiver, signal, switch hook, and keys for the other stations, talking circuits interconnecting said stations, a common battery for supplying talking current to all of said talking circuits, a relay at each station in the circuit of the signaling current to any station called, saidrelay having a contact by which talking circuits from such station to other stations can be exclu` sively established, and means for maintaining said talking circuits completed after the termination of the signaling current.

3. Infa secrecy intercommunicating telephone system, a plurality of stations each having a transmitter, receiver, signal, switch hook, and keys for the other stations, talking circuits interconnecting said stations, a common battery for supplying talking current to all of said talking circuits, a i'e'lay at each station in the circuit of the vsignaling current to any station called, said ing a contact by which talking circuits from such station to other stations can be exclusively established, and means for inaintaining said last mentioned contact closed after the termination of the signaling current.

5. In a secrecy intercoinmunicating telephone system, a plurality of stations, each having a transmitter, a receiver, signal, switch hook, and keys for the other stations, a relay at each station in the circuit of the signaling current to any station called, said relay having a contact by which talking circuits from such station to other stations can be exclusively established, and a mechanically opened contact for breaking such talking circuits and means for opening said contact when any key is displaced oi' the re-I ceiver is placed on the hook at the calling station.

6. In a ,secrecy intercoininunicating telephone system, a plurality of stations each having a transmitter, receiver, signal, switch hook, and keys forthe other stations, a relay at each station in the circuit ot' the signaling current to any station called, said relay having a contact by which talking circuits from such station to other stations can be exclusively established, and a incchanical connection from the keys and also from the said switch hook for interrupting the talking circuits whenever any key is displaced oithe receiver placed on the hook.

7. In a secrecy intcrcoinmunicating telephone system, a plurality of stations each having a transmitter, receiver, signal, switch hook, and keys for the other stations, talking circuits interconnecting said stations, a common battery for supplying talking current to all of said talking circuits, a relay at each station in the circuit of the signaling current to any station called, said relay having a contact by which talking circuits from said station to other stations can be exclusively established, and a shunt circuit including a resistance automatically bridged acrosssaid relay when the latter is operated. y

8. In a secrecy intercommunicating telephone system, a plurality of stations each having a transmitter, receiver, signal, switch hook, and keys for the other stations, talking circuits interconnecting said stations, a common battery for supplying talking current to all of said talking circuits, a relay at each station in the circuit of the signaling current to any station called, said relay having a contact by which talking circuits from said station to other stations can be exclusively established, and a circuit for holding said relay when the latter is operated.

9. In a secrecy intercominunicating telcplione system, a plurality of stations each having a transmitter, receiver, signal, switch hook, and keys for the other stations, talkriaaaaa common battery for supplying talking cur? rent to all of said talking circuits, a.relay at each station in the circuit of the signaling current to any station called, said relay having a contact by which talking circuits from such station to other stations can be exclusively established, and a Contact closed by the removal of the receiver from the hook for maintaining .said relay operated after it has been initially operated.

10.l In a secrecy intercommunicating telephone system, a plurality of stations each having'a transmitter, receiver, signal, switch hook, and keys for the other stations, talking circuits interconnecting said stations, a common battery for supplying talking current to all of said talking circuits, a relay at each station in the circuit of the signaling current to any station called, said relay having a contact by `which talking circuits from such station to other stations can be exclusively establishedfand a branch circuit completed by the removal of the receiver from the hook and by the operation of the relay for maintaining said talking circuit closed after the initial operation of the relay.

- 11. ln a secrecy intercommunicating telephone system, a plurality of stations each having a transmitter, receiver, signal, switch hook, and keys for the other stations, a relay to each station in the circuit oit the signaling current to any station called, said relay having a contact by which talking circuits from such station to other stations can be .exclusively established,"and a l'oW reactancey shunt automatically bridged around said relay for the signaling current.

12. lln a secrecy intercommunicating telephone system, a plurality of stations each having a transmitter, receiver, signal, switch hook, and keys for the other stations, and a relay to each station in the circuit of the signaling current to any station called, said relay having a contact by which talking circuits trom such station to other stations can be exclusively established, a low reactance shunt automatically bridged around said relay for the signaling current, and a branch circuit yfor keeping the relay operatedysaid last mentioned branch `circuit being interrupted by the displacement of any station key in any direction.

13. In a secrecy intercommunicating telephone system, a plurality of stations each having a transmitter, receiver, signal, switch hook, and keys for the other stations, a relay at each station in the circuit of the s1gnaling current to any station called, said relay having a contact by which talking circuitsfrom such station to other stations can be exclusively established, a branch circuit from said relay completed by said relay and by the removal of the receiver from the hook for maintaining said relay operated after the termination of the signaling current, said last mentioned branch circuit being interrupted by the displacement of any station key in any direction at the calling station.

14. In a secrecy telephone system, a plurality of stations each having a transmitter,

receiver, signal, a switch, and selective station connecting devices for the other stations, and a relay at each station in the circuit of the signaling current to a station called, said relay halving a contact by which talking circuits from such station to other stations can be established independently of the station selective devices at the other stations.

I 15. In a secrecy telephone system, a plurality of stations each having a transmitter, receiver, signal, a switch, and selective station connecting devices for the other stations, a relay at each station in the circuit of the signaling current to a station called,

said relay having a contact by which talking circuits from such station to other stations can be established independently of the station selective devices at the other stations, and means for maintaining said talking circuits completed after the termination of the signaling current.

16. ln a secrecy telephone system, a plurality of stations each having a transmitter, receiver, signal, a switch, and selective station connecting devices for the other stations, a relay at each station in the circuit of the signaling current to a station called, said relay having a contact by which talking circuits from such station to other stations can be established independently of the station selective devices at the other stations, and means for maintaining said relay operated after termination of the signaling current.

17. lln'a secrecy telephone system, a plurality of stations each having a transmitter,

receiver, signal, a switch, and selective station connecting devices for the other stations, a relay at each station in the circuit of the signaling current to a station called, said relay having a contact by which talking circuits from such station to other stations can be established independently of the station selective devices at the other stations, and means for maintaining said last mentioned contact closed after the termination of the signaling current.

18. ln a secrecy telephone system, a plurality of stations each having a transmitter, a receiver, signal, a switch, and selective station connecting devices for the other stations, a relay at each station in the circuit of the signaling current to a station called, said relay having a contact by which talking circuits from such station to other stations can be established independently of the station selective devices at the other stations, and a mechanically opened contact for breaking such talking circuits when any key is displaced.

19. In a. secrecy telephone system, a plurality .of stations each having a transmitter, a receiver, signal, a switch, and selective station connecting devices for the other stations, a relay at each station in the circuit of the signaling current to a station called, said relay having a contact by which talking circuits from such station to other stations can be established independently of the station selective devices at the other stations, and a -mechanically opened contact for breaking such talking circuits when any selective station connecting device is displaced or the said switch operated at the calling station.

20. In a secrecy telephone system, a plurality of stations each having a transmitter, receiver, signal, a switch, and selective station connecting devices for the other stations, a relay in the circuit of the signaling current to a station called, said relay having a contact by which talking circuits from such station to other stations can be established independently of the station selective devices at the other stations, means for maintaining said talking circuits completed after the termination of the signaling current, and means for interrupting the circuit of said relay when any selective station connecting device is displaced at the calling station or the said switch operated.

21. In a secrecy telephone system, a plurality of stations each having a transmitter, receiver, signal, a switch, and selective station connecting devices for the other sta,- tions, a relay at each station in the circuit of the signaling current to a station called, said relay having a contact by which talking circuits from such station to other stations can be established, and a mechanical connection from the station selective devices and also from the said switch for interrupting the talking circuits whenever any selective station connecting device is displaced or the said switch operated.

22. In a secrecy telephone system, a plurality of stations each having a transmitter, receiver, signal, a switch, and selective station connecting devices Jfor the other stations, a relay vat each station in the circuit of the signaling current to a station called, said relay having a contact by which talking circuits from said station to other stations can be established independently of the sta- `tion selective devices at the other stations,

and a shunt circuit including a resistance automat'ically bridged across said relay when the latter is operated.

23. In a secrecy telephone system, a plurality of stations each having a transmitter,

receiver, signal, a switch, and selective station connecting devices for the other stations, a relay at each station in the circuit of the signaling current to a station called, said relay having a contact by which talking circuits from said station to other stations can be established independently of the station' selective devices at the other stations, and a circuit for holding said relay when the latter is operated.

24. In a secrecy telephone system, a plurality of stations each having a transmitter, receiver, signal, a switch, and selective station connecting devices for the other stations, a relay in the circuit of the signaling current' to a station called, said relay having a contact by which talking circuits from such station to other stations can be estab'- lished, and a low reactance shunt automatically bridged around said relay for the signaling current.

25. In a secrecy telephone system, a plurality of stations each having a transmitter, receiver, signal` a switch, and selective station connecting devices for the other stations, and a relay inthe circuit of the signaling current to a station called, said relay having a contact by which talking circuits from such station to other stations can be established,'a low reactance shunt automatically bridged across said relay for the signaling current, and a branch circuit for keeping the relay operated, said last mentioned branch circuit being interrupted by the displacement of any Selective station connecting device in any direction.

26. In a secrecy telephone system, Aa plurality of stations each having a transmitter, receiver, signal, a switch, and selective station connecting devices for the other stations, a relay in the circuit of the signaling current to a-station called, said relay having a Contact by which talking circuits from such station to other stations can be established independently of the station selective devices at the other stations, a branch circuit from said relay completed by said relay and by the removal of the receiver from the hook for maintaining said relay operated after the termination of the signaling current, said last mentioned branch circuit being interrupted by the displacement of any selective station connecting device in any direction at the calling station.'

In testimony whereof, I have hereunto set my hand, in the presence of two subscribing witnesses.

WALLACE PFAU ANDRJcK.

Witnesses: f

D. S. MALLonY, CHAs. WELLNER. 

